“Prime” refers to the ability of the pump to fully circulate water from the pool, to the pump and filter, and then back to the pool. If the pump does not prime, the water within the pump continues to get hotter and hotter, eventually warping the pump basket and possibly doing other damage to the equipment. Not to mention the fact that your pool will be sitting without circulating or filtering, basically stagnating.
There are a number of factors that could be causing this situation. It could be due to clogged/full skimmers, debris over the main drain in the pool, a leak in the plumbing, low water level in the pool, or an extremely dirty filter, First, check all valves in front of the pump to ensure they are open so that water can enter the pump. Verify that water level is at least halfway up the tile line. Sometimes a skimmer weir (the floating door in front of the skimmer) is stuck, creating a dam that prevents water from entering the skimmer.
Also, empty your skimmer baskets on the side of the pool. During autumn months, an overabundance of leaves can clog up the skimmers, and in other times, windblown debris (plastic bags) can cover skimmer completely. Open your pump and empty the pump basket. Examine the lid o-ring. If broken or cracked, replace it. Before you close the lid, fill the pump with water. Once lid is secure, turn it on. If it doesn’t catch prime within the next minute or so, there are other things you will need to do.
Once you have gotten to this point, if pump still hasn’t primed, it will be necessary to dig a little deeper. Sometimes, if water level had been low or flow was restricted, there is air in the line. DO NOT attempt to use a compressor to clear the lines, as this will only worsen the problem. A simple yet effective trick is this: With the pump turned off, open up the pump. Close the valves in front of the pump.
While filling the pump up with water and maintaining it completely full, open and close the valves repeatedly, back and forth. If there is air in the line, when you open, then close the valve, you will see a “burping” action with the water. Each open and close action will force more water from the lines. When you can no longer get it to burp, close the lid, open the valve, and turn on the pump. If there are more than one suction line, I suggest you open only one till pump is fully primed, then open the other one at a time.
This will resolve the majority of pump prime problems. If it doesn’t, you could have a valve leaking. Replacing the o-rings will usually resolve this problem. If nipples in front and on top of pump are leaking, they will need to be replaced. I suggest using only Schedule 80 CPVC, as they will endure more heat. Be sure to seal them with Teflon, and a thin layer of silicone on top of Teflon makes for a better seal. If filter is dirty, backwash and do a thorough filter clean ASAP.